K H V +■ . c • r 



567 
) E3 
>y 1 



L 



REPORT 



ON 



FERTILIZATION 



BY 



Charles F. Eckart 

CHAIRMAN OF COMMITTEE 



SUBMITTED TO THE 



Hawaiian Sugar Planters' Association 



NOVEMBER, 1901. 



HONOLULU: 

HAWAIIAN GAZETTE CO. 

1901 



REPORT 



ON 



FERTILIZATION 



BY ^ 



Charles F. Eckart 

CHAIRMAN OF COMMITTEE 



SUBMITTED TO THE 



Hawaiian Sugar Planters' Association 

No^yy^^^^ 1 90 1. 



HONOLULU: 

Hawaiian Gazette Co. 

1 90 1 






Committee on Fertilization 



C V. ECKART, 

C. M. AValtox, 
J T. Ckawlby, 
Geo. Koss, 
John Watt. 



9^\ 



REPORT 

ON 

FERTILIZATION 



(C. F. ECKART, Chairman of Committee) 



H(iNOLT Lu, H. T., November IStli, 1001. 

To THE PkESIDEXT. TRUSTEES, AND MEMBERS OF THE HAWAIIAN" 

SuoAR Planters' Association, 
Honolulu, T. H. 

Gentlemen: — Dnrino- the past year, no less than twenty-five 
thousand tons of commeroial fertilizers have been added to 
our Hawaiian soils to satisfy the demands of the suoar in- 
dustry. 

The initial cost of this large quantity of fertilizing material, 
added to the cost of distybution and application, makes the 
subject of fertilization from all "economic standpoint one of 
great importance and-- wSrtl^v 'oC't'lose consideration. The 
comparative cost of the different manurial compounds, their 
relative efficacy in meeting the requirements of the cane crop, 
their proportional liability to waste under given climatic con- 
ditions, combined with a knowledge of the soil to which they 
are to be applied, must constitute the only basis from which 
any rational and economical system of fertilization can be 
derived. 

The earliest method in use for determining the ability of a 
soil to furnish the requisite amount of plant food for a giveu 



fi'O]), involved ]»iactical tests with small field i)lats. On a 
small area, without fertilization, but with due obscnvance of 
proper tilth and cnltivation. a crop was started for puri)os<..^s 
of comjiarison. At the same time other |)lats Avere laid off 
in the same field and i-eceived alotments of nitro<ien. i)hos- 
jthoric acid, lime, ]»otash, etc.. and the effect of each one of 
these applied elements was carefnlly noted as regards any in- 
crease of the given crop over and above that on the nnfertil- 
iz(Ml ai-ea. Xol only were these fertilizers added separately oi\ 
some plats, but in mixtnres of varying })rop()rtions on others, 
and valuable conclusions v.ere reached as to the demands of 
the i)lant. These jjractical tests are still carried on to a large 
extent in some agricultural communities, and results are 
I'eached of sufficient value to more 1han compensate the farui- 
er for time and labor expended. 

These ])lat ex]>eriments, however, are found to be open to 
the following objection: Tlie time necessary to determine th(' 
proper quantity and the best balanced ])ioportion of fiMtiliz 
ing- ingredients to be added for maximum yields, covtns per- 
iods of considerable length. 

The chemist has endeavored to overconu* this objiM-tion, and 
to reach in the laboratory results thai Inne taken the agricul- 
turist months to learn from observation in tin/ fi(dd. l>y an 
examination of the ash of the ])articular plant to be groAvn. 
he learned the cpiantities and ]>rop(irtions of the various min- 
eral elements thai had been removed from the soil, and used 
in the development and elaVolfitum of the ]tlant and its ])ro- 
ducts. He digested a sniail (juanlity of the soil in hydro- 
ciiloric acid of a certain sjx'cific gravity, and noted the ]»er- 
centages of the different eleuu^nts in the resulting soil extract. 
From thes(^ analyse s. conclusions were drawn as to the fertil- 
ity of the land in question, and the supply of ]»lant food, from 
which the cio]) could draw as m^'ded. was su])])osed to have 
been nu^asui-ed. 

Unfortunately, (liscrei)ancies soon begin to arise between 
field results with 1 he growing cro]> and the conclusions 
reacluMl from chemical analyses, and the chemisi found that 



liii-' slioi'tt'i- method was not witlimit palpaltlc defects. If an 
element was lackin<i in the soil or was ])i'esent in very small 
quantity, he felt safe in i-ecommendinji- the apitiication of that 
element in fertilization, bnt where an in<>redient was i)resent 
in lar<ie amounts, he sometimes found that that self-same 
element was one to be added in manurial mixtures for satis- 
factoiy results. In othei- words elements ean be present in 
larjie amounts in the soil, but in a state whieli renders them 
unavailable to the plant. Ke^arding the ordinary agricultural 
method for determining soil deficiencies, this max be said in 
its favor: That in some instances it serves as a valuable guide 
in fertilizer recommendations, when the chemical analysis is 
supplemented with reliable data as regards the physical con- 
dition of the soil, combined with a knowdedge of the climatic 
conditions of the locality from which the sample has been ob- 
tained. 

In view of the objection which has been mentioned regard- 
ing the agricultural method, investigators have endeavored to 
find an acid nuire suitable for soil digestion than hydrochloric, 
and one whose solvent action would be more comparable with 
the acids of the plant roots. Organic acids were substituted 
for mineral acids in the experiments, and a long stride was 
taken towards the solution of this important problem. 

Asi'AUTic Acid Miothod. — This method of determining the 
availibility of the plant food in the soil, is the one at present 
in use at the Experiment Station, and a few words may be 
said in regard to its practicability for Hawaiian conditions. 
The credit for this system of soil investigation belongs to Dr. 
Walter Maxwell, the former director of the Experiment Sta- 
tion, and ]Mr. J. T. Crawley, and is the result of a close and 
scientific study of conditions obtaining on these islands. A 
detailed account of the work along this line and the logical 
conclusions drawn from the same, may be found in an article 
on "Lavas and Soils of the Hawaiians Islands," published by 
Dr. Maxwell in 181)S, and in this rejsort only a brief reference 
to the deductions will be made. 

Tlu^ amount of mineral matter being carried into the sea 



by waters of discliarge from the land was determined with 
the following results: 

Hawaiian Waters. 

Lime 0.0013 Per cent 

Potash 0.0005 Per cent 

Phosphoric acid : 0.0001 Per cent 

These figures represent the average mineral content of Ha- 
waiian waters collected at many places considered suitable 
for such observations. 

An analysis was made of upland cropped and corresponding 
virgin soils, the average results being as follows: 

UPLANDS. 



Elements 


Virgin 


Cropped 


Loss 


Lime , 

Potash 

Phosphoric Acid. 


Per cent. 
0.415 
324 

248 


Per cent 
0.248 
0.270 
0.243 


Per cent. 

40.20 

16.60 

2.02 



The term cropping as applied to the above table is used in a 
very general sense. It includes the action of rain, cultivation, 
and growing crops in removing plant food from the soil. 

Data were obtained which showed that in one case where 
7,000 lbs. of lime were removed per acre, only about 15 per 
cent of this amount had been utilized by the crop itself, and 
in respect to potash the crop took only one-half of the amount 
removed by total cropping. "These data show that any sys- 
tem of judging of the depletion or of restoring the fertility of 
soils, that is based upon a mere calculation of the amounts of 
the elements that are carried away from the land in crops, is 
devoid of any approach to the actual facts of the matter." 
The reason that upland virgin and cropped soils were taken 
for this comparison, was on account of the washing action of 
the rains. The niakai soil receives a large part of the wash 
from the mauka lands, and in some instances cropped soils 
on the lower lands show a higher proportion of given elements 
than the virgin. The amount of lime removed by cropping is 



40.2 ])vv cent, and if this is taken as a standard, applyinj; it also 
as a basis for the waters of discharjie, the relations existing 
between it and the other elements mav be tabulated as below: 



Elements Removed from the Soil in 
Water. 



Lime 
Per cent. 

40 2 



Per cent. 
15.1 



Phosphoric 
Acid 



Per cent. 
2.80 



Elements Removed from the Soil by 
Cropping. 



Lime 



1 otash 



Per cent 
40 2 



Per cent. 
16 6 



Phosphoric 
Acid 



Her cent. 
2 02 



As Dr. ^Maxwell has j>ointed out, these results do not ajtpear 
so remarkable, when it is consideivd that the great bulk of 
matter removed by total (•r(>]»]»ing is found in the wateis of 
discharge. 

AVith these data at hand, the next step was to tiiid some 
acid whose solvent action on the soil would remove the essen- 
tial elements in proportions a{)proximating those of cro])ping. 
Many organic acids of different strengths were allowed to act 
on the soil for varying lengths of time, and it was found that 
an one per cent solution of aspartic acid, when shaken with 
the soil at intervals during twenty-four hours, apparently met 
all requirements. The amounts and proportions of the ele- 
ments, removed by this acid dui-ing twenty-four hours, were 
approximately the same as were removed by total cropjjing 
during a period estimated at twenty years. Dr. Maxwell's 
conclusions were stated as follows: "An one per cent solu- 
tion of aspartic acid takes out of Hawaiian soils in twenty- 
four hours, the same amounts of lime, potash, and prosphoric 
acid, that are removed during the production of ten crops of 
cane. Therefore one-tenth of these amounts may be taken a« 
the i»roi)ortions of lime, ])otash, and phos])horic acid that are 
available for the iir.mediate cro]) of cane." The Aspartic Acid 
Method, although not i»erfect, offers a fairly reliable means for 
determining the amount of available ])lant food in the soil, 
and is in fact a better guide in the matter of fertilization on 
these islands than any other known method, as in its concep- 
tion. Hawaiian conditions intliienced every consideration. 



6 

Before considering the subject of fertilization in its more re- 
stricted sense, i. e. the ap|>lication of ditterent niaiuirial com- 
pounds to tlie soil, itrobably a few words on the average avail- 
ability of the essential elenn^its in (question might i)i-ove of 
interest. 

AvAiLABiLri'Y OF Elkmexts. — ('ousiderable data are at hand 
to give an ad(Miuate idea of the amounts of lime, potash, phos- 
phoric acid and nitrogen that are present in the soils of the 
respective islands, the subjoined table representing average 
results of about one hundred analvses. 



ISLAND 


Lime 

380 
418 
0.395 
0.185 


Potash 


Phosphoric 
APid 


Nitrogen 


Oahu 

Kauai 

Maui 

Hawaii 


0.342 
0.309 
357 
0.346 


207 
0.187 
0.270 
0.513 


176 
0.227 

0.388 
0.540 



These results wer<^ obtained by the ordinary agricultural 
method, which was in use at the Experiment Station prioi- to 
the adoption of aspartic acid as a soil solvent, and although 
an absolute analysis would give somewhat larger results, 
these are couiparative to a large extent as showing the pro- 
portions of lime, potash, phosphoric acid, and nitrogen present 
in the island soils. 

The amounts of the mineral ingredients which are found to 
be available are as follows: 



ISLAND 


Lime 


Potash 


Phosphoric Acid 


Oahu 

Kauai 

Maui 

Hawaii 


Per cent. 
.01568 
.01367 
01764 
.00789 


Per c-ent. 
.00256 
.00249 
00312 
.00156 


Per cent. 
.00012 
.00013 
.00012 
.00014 



or reducing these pei-centages to a more tangible form, we 
have: 





ISLAND • 


Lime 


Potash 


Phosphoric 

4 2 lbs, 
4.5 " 
4.2 " 
4.9 " 


Acid 


Oahu 

Kauai 

Maui 

Hawaii 


549 lbs. 
478 '• 
617 " 
276 " 


89 lbs. 
87 " 
109 " 
54 " 





which quantities rei)iesent the amounts of the essential min- 
eral elements, in one acre of soil to a depth of one foot, that 
are in a condition to be removed through the several actions 
of total cropping, during the growth of one crop. 

It is interesting to note that Kauai stands highest in lime, 
Maui in potash, and Hawaii in phosphoric acid. The smallest 
percentage of lime is on Hawaii, while Kauai is lowest in 
potash and phosphoric acid. 

If, however, we consider the availability of these elements 
instead of the actual amounts in the soil, a somewhat modi- 
fied order presents itself: Maui and Oahu are both higher iu 
available lime than Kauai, Oahu standing first. INIaui with 
the highest total content of potash has also more of that 
element iu an available form than the other islands. The 
amounts of available phosphoric acid show little variation, 
notwithstanding a difference between .187 per cent total phos- 
phoric acid on Kauai, and .51o per cent on Hawaii. This 
latter ingredient is so closely bound up in iron and aluminic 
compounds as to be practically insoluble; on Hawaii nine tons 
of the element per acre scarcely yield five })ouuds in an assim- 
ilable foi'm. 

Having considered the metliod in use for gauging the avail- 
ability of the mineral elements in question, and having noted 
the amounts in which they are present in the soils of the 
respective islands, we will next consider the demands of tlu- 
cro]). 

Elkmioxts Removed by the Cuoi'. — In the rejxtrt of the 
Experiment Station for 1!HMI, it was pointed out that where 
29,010 lbs. of sugar were produced i)er acre by Lahaina cane, 
6,60(> lbs. of mineral matter were extracted from the soil, 
while with Rose Bamboo, 30,475 lbs. of sugar required 7,662 



lbs. of inineral matter. The following t^ible shows the 
amounts of the various elements includinjj;- nitrogen, which 
were required to produce one ton of sugar by the respective 
varieties: 



Varieties 


Nitrogen 

25.4 lbs. 
40 5 " 


Phosphoric 
Acid 


Potash 


Lime 


Lahaina 

Eose Bamboo .... 


16.0 lbs. 
13.6 " 


89.5 lbs. 
114.2 ' 


28 7 lbs. 
34.8 " 



If we should take live tons of sugar per acre, as the average 
production for the Hawaiian Islands, and consider for our pur- 
pose that the amounts of the essential elements required by 
the croj) for such a yield would be Ihc same as at the Experi- 
ment Station, we have: 

Nitrogen, Phosphoric Acid, Potash, and Nitrogen Required 
bv the Cane to Produce Five Tons of Sugar 



Varieties 


Nitrogen 


Phosphoric 
Acid 


Potash 


Lime 


Lahaiaa 

Kcse Bamboo 


127.0 lbs. 
202.5 " 


80 IbB. 

68 " 


447 5 lbs. 
571.0 " 


143 5 lbs. 
174.0 " 



x\s it is our present ])urpose to consider crop reijuirements 
in general, and not the special demands made by particular 
varieties, we will take the mean of the figures presented 
above, as representing Lahaina and Rose Bamboo needs, and 
for future consideration say, that a crop to produce five tons 
of sugar, would require per acre, about: 
1()4.7 lbs. of nitrogen. 

74.0 lbs. of phosphoric acid. 
509.2 lbs. of potash. 
158.7 lbs. of lime. 
We will next compare the amounts of available elements in 
the soils of the respective islands, with the amounts of these 
elements that would be required by a crop producing five tons 
of sugar. The nitrogen contents of the lands are not given. 



9 

as at the present time we have no reliable method for deter- 
ininiiiii its availabilitv. 



ISLAND 


Lime 
in soil 


Lime 
required 
by crop 


Potash 
in soil 


Potash 
required 
by crop 


".'• A"d ; required 
m sou y,^ crop 


Nitrogen 
required 
by crop 


Oahu 

Kauai 

Maui 

Hawsiii 


Pounds 
549 
478 
617 
276 


Pounds 

CD 
1— 1 


Pounds 

89 

87 

109 

54 


Pounds 

o 


Poi'.nds Pounds 
4.2 

4.5 ^ 
4 2 "^ 
4 9 


Pounds 

CO 



It will be noticed from tht' above figures that lime is the 
only one of the elements that would appear to be present in 
sntticient quantity for the needs of the crop. But when we 
consider the statement previously made, concerning the small 
proportion of lime that is taken up by the cro]) on some up- 
land soils as comitariMl with the proportion removed by the 
other factors involved in total croitping. we may see that the 
average lime content is not so large but what we must con- 
sider it very carefully. Maui stands highest in available lime, 
having r»lT lbs. on an average to the acre, but if only 15^/ of 
that amount could be utilized by the crop, as in the instance 
above referred to (which was most likely an extreme case), 
only !>2.55 would go to the crop where 104.7 lbs. were needed. 
Even if tlu' cane gets on an average 30 per cent of the lime 
removed, but small margin would be left on Maui, above 
actual crop requirements, while on Oahu there would be just 
enough, and on Kauai and Hawaii a marked deficiency. 

The i»otash is found to b<' very much too low on all the 
islands for su])i)lyiiig the wants of the cane, and it is readily 
seen why it was found necessary, during recent years to in- 
crease the proportion of that element in fertilizers applied. 

Concerning i»hos}»horic acid, the dearth of this element in 
available quantities in our island soils is very a]»])arent, but 
we are almost convinced that the aspartic acid method for soil 
analysis would indicate this ingredient to be lower in avail- 
ability than it really is. 

In the consideration of the amount of plant food taken from 



10 



the soil by the growing- crop, iu order to ]>iodiU'e one ton of 
sngnr, we took an average of the (piaiitities removed by 
Lahaina and Rose Bamboo varieties, as giving a fair idea of 
the large demands made by the cane ni)on the soil. However 
these proportions and amonnts are not to be taken as rejjre- 
senting the exact requirements of the cane in any locality or 
under any conditions. At the Exjieriment Station, tlie figures 
in (juestion were reached in a comjtarative test of thirteen 
varieties of cane, grown under similar conditions as regards 
soil, fertilization, and climate, one of the objects being to nott^ 
their resj)ective drafts on the soil as compared with their 
value as producers of sugar. 

MixEi{.\i, Mattku Retuknkd to the Koil in Cane Refuse. — 
The last table, although it gives an idea of the amount of 
plant food that would be required for a crop of such size as 
was under consideration, does not show the quantities of lime, 
phosphoric acid, potash and nitrogen, that are taken away 
from the field. If it did, the application of artificial manures 
from crop to crop would reach much larger proportions than 
it really does. As a matter of fact, after the cane is cut for 
the mill, and the trash and dead canes, etc., are burned, as is 
most generally the case on plantations, a much larger amount 
of mineral matter is returned to the soil than is generally 
supi)osed. By burning, of course, all the nitrogen is lost with 
its corresponding manurial value, l)ut tlie other essential 
elements remain on the field to be used largely by the succeed- 
ing crop. 

The following figures indicate the relative amounts of the 
elements found in the tops, etc., and in the cane, per ton of 
sugar grown at the Exj)erinumt Stati(»n. 

ELEMENTS REMOVED FROM SOIL PER TOS OF SUGAR 

PRODUCED. 



ELEMENT 


rn tops, leaves, and 
dead canes. 


In cane 


Lime 

Phosphoric Acid 

Potash 


27.9 lbs. 

6.5 " 
66.5 " 
20.2 " 


3.7 lbs. 
8.2 " 
85 3 '• 


Nitrogen 


12 7 " 









11 

These results sliow tlic lime in tlu^ lojtS'. etc. to be over 
seven tinu^s tliiit in the cane; the idiosjihoric acid is nu)re 
evenly balanced; while the tops, etc., have nearly twice as 
mnch i)()tasli as the <-ane. It is thus seen that if only one- 
half of the mineral matl<'r in the refuse of the tield is con- 
served, a nianurial mixture is added to the soil of ])articular 
value, which would less(ui to a larj;e extent the amount to be 
apjdied dnriuL', I'ciiular fertilization. 

In regard to the comparative availability of those elements 
returned to the soil thronj^h the burning;- of the trasli, and the 
same added in ordinary fertilization, there is sonu^ ditt'orence 
in favor of the latter. The potash in the ash is chietly in the 
form of chloride, with a smaller amount as carbonate and 
silicate, and the chloride is as assimilable as any that could 
be addfHl in nianurial mixtures. The phosphoric acid is rt'- 
turned to the land as iron and aluminic ]>hosi)hates with a 
much smaller amount as phos|»hate of lime, and i)hos])hate of 
majiuesia. These ])hos]»hates are nu)re insoluble than those 
••enerally added in fertilizers and are not imnuHliately avail- 
able to the i»lant. The linn^ in the ash is nu)st likely com- 
bined with silica. ]thosi)horic acid, and sulphuric acid and is 
only slijihtly soluble. 

FOKMS IN \\'Hn'H PlOUTlLlZIX*; IX(;UEI)IKX'1'S AUK Al'l'LIKIi. 

Tlie amount of available jdant food in the soil and the prol>a- 
ble requirements of the crop to be grown are im]((H'tanl fac- 
tors. to be considei-ed in any estimation of manurial needs. 
However, nnlet-s these data are su]tplemeuted by a knowledge 
of climatic conditions, and a jtroper regard shown f(n- their 
several intluences, analytical investigations in res])ect to the 
nature of the soil are often of litth^ value. 

To the action of the heavy i-ains of the ui)lands in washing 
away the more soluble ingredients of the soil we have already 
i(4Vrred. Thf^se rains not only leaeh out material which is 
gradually being reiulered available for ])lant uchmIs, but also 
that which is artittcially a]>i»lied in tln^ form of fertilizers. 
The ei-osiv(^ action on the natural matei-ial of the land cannot 
be controlled, but with a (Ww consideiation of the ]»hysical and 



12 

cheiuical piopeities of applied ingredients, we can place in the 
soil those substances required by \he plant, and in a form 
least liable to waste. 

We now come to a consideration of the elements themselves, 
the relative efficacy of their various combinations, and the 
conditions that influence their selection as component parts of 
manurial compounds for different locations. 

Nitrogen. — This element is applied to the land in three 
forms, namely as nitrate of soda, sulphate of ammonia, and 
organic substances. 

Nitrate of soda is the most soluble of these three forms and 
besides holds its nitrogen in the most assimilable condition. 
Solubility and availability are not necessarily synonomous 
expressions as regards nitrogen compounds, although the lat- 
ter condition is greatly influenced by the former. The solu- 
bility of nitrate of soda is influenced by the temperature of the 
solvent, at 78" Fahr., 300 parts of water dissolve t)(l.:^;{ parts of 
nitrate. Added to this extreme solubility is an unfortunate 
disinclination of the acid part of the salt to become fixed in 
the soil, which causes its use on some lands to be attended by 
considerable risk on account of the leaching action of the 
rains. 

A test was conducted at the Experiment Station in 181)8 to 
determine the relative liabilities to waste of nitrogen in the 
form of nitrate of soda, and the same element in the form of 
sulphate of ammonia. In one instance 200 grams of nitrogen 
as nitrate of soda and in another the same amount as sulphate 
of ammonia were added to corresponding soils draining into 
a lysimeter. Forty-eight hours after the application of these 
compounds, a copious irrigation was allowed to over-saturate 
the soil, and the excess of water was collected in a receiver 
and analyzed. The loss in nitrogen is seen by the following 
rable: 



13 



Forms 


Nitrogen Applied 


Nitrogen lost in water 
As Nitrate As Ammonia 


Nitrate of Soda 

Sulphate of Ammonia 


200 grams 
200 " 


72. 5G grams 
3 08 " 


0.00 grams 
0.44 " 



The loss of nitroj;eii from nitrate is very large. Of the 
nitrogen fiom sulphate of auinionia only a minute piopordou 
was found in the receiver, the major part of this small quan- 
tity being in the form (ff nitrate, into which state it iia<i been 
converted by the nitrifying organisms of the soil. 

Mr. J. T. Crawley, of the Committee on Fertilization, con- 
ducted a number of interesting experiments during the first 
part of this year, for the purpose of obtaining data as regards 
the retentive power of "sandy soils" for fertilizers and water, 
and his results are of particular value in a consideration of 
the subject in hand. Four soils varying in their pi'0]»ortions 
of lime carbonate from 71.25 per cent to 91.07 per (ent were 
placed in iron pipes two feet six inches long and one inch in 
diameter, the i)ipes being filled to within six inches of the top. 
One gram each of ammonium sulphate, nitrate of soda, and 
muriate of potash were dissolved in a liter of water and 500 
cubic centimeters of this solution holding one-half gram each 
of the salts mentioned were poured upon the soils and allowed 
to drain through. It was found in regard to the nitrat(^ of 
soda that practically none was retained by any of the soils, 
while the other compounds were fixed in an inverse proportion 
to the lime carbonate content of the medium through which 
they filtered. In a consideration of the action of sulphate '»f 
ammonia and sulphate and muriate of potash when a[)plied to 
the soil, we shall have occasion to again refer to Mr. Craw- 
ley's interesting experiments. 

The readiness with which nitrate of soda may be taken ui) 
b,y excessive rains or irrigation and carried from the land is 
readily seen, but bound up with this question is another of 
almost equal inq)<)rtance. When the nitrate is lost from the 



14 

land Ihiough the ((vei-saturation of its soil, not ouly so much 
nitrogen is lost, but likewise a hirge amount of lime. The 
nitric acid of the nitrate on coming in contact witli the \bne 
of the soil, forms lime nitrate, which is almost as easily solu- 
ble and as readily washed out as the nitrate of soda. 

To observe this action of nitrate on lime, as well as the rel- 
ative action of different salts in the same particular, tests 
were made at the Experiment station in connection with 
other lysimeter investigations. Niti-ate of soda, chloride of 
potash, ammonium sul])hate and sulphate of potash were ap- 
plied to the rows of cane growing over the lysimeter drains, 
and forty-eight hours later these rows were irrigated with 
102 gallons of water, of which (juantity 38 gallons leached out 
and was analyzed. 



Drain 


Salt applied 


Lime Lost 


No. 1 


None 


1 . 72 grams 


No. 2 


Nitrate of Soda 


26.52 " 


No. 3 

No, 4 


Chloride of Potash 

Sulphate of Ammouia 


23 49 " 
5 . 49 " 


No. 5 


Sulphate of Potash 


2.73 " 



The lime taken out through the influence of nitiate is seen 
to be extremely high> 

AVe have spoken at some length concerning the unfavorable 
characteristics of niti-ate of soda Avhen applied to lands of 
heavy and uncertain rainfall, parriculaily when such lands 
are deficient in lime. However. notAvithstanding these several 
draw-backs to its general use in all localities, nitiate of soda 
has suflficient su]terior qualities when ai>])lied in juoper (pian- 
tities and under suitable conditions to render its use of the 
highest advantage. 

AMien ap])lied in large amounts and under such conditions 
as to allow of the fullest effects, nitrate has Ix^ni observed in 
many instances to induce an abnormal and undesirabh^ 
growth, which retarded the ripening of the cane, and resulted 
in juices of low purity and low sugai- contenl. On th(^ other 



15 

band this selfsame stiniulatiii^- property lias been of the 
greatest service to yellow and "nitrojien-hunjiiy" cane, and 
with the application of small amounts of this material, won- 
derful tonic effects have been produced in an extremely short 
space of time. 

In rej^ard to the influence of nitrate on tassel ing, Mr. Geo. 
Renton of Kwix Plantation writes: "My experience in one 
case with a late application in September of nitrate of soda 
was that it materially effected tasseling. About one-third 
only of the stalks flowered. As the application in this instance 
was made for the express purpose of preventing the tasseling 
of the cane, these results were gratifying.'' Mr. Kenton fur- 
ther says: "It is my opinion that either excessive or late ap- 
plications of nitrate of soda will lower the juice purity. The 
best juice obtained at this mill was from canes upon which 
nitrate was put on not later than the latter part of April." 
The experience of Mr. Olding at Kohala has been that 
"nitrates prevent tasseling in a very marked degree." It was 
observed last year at the Experiment Station that nitrogenous 
fertilizers in general prevented tasseling during the flowering- 
period, whereas, unfertilized plats, and plats receiving merely 
IJotassic and phosphoric acid fertilizers flowered without ex- 
ception. On account of the readily available condition of 
nitrate of soda we should expect small applications of this 
material to exert a more potent influence in preventing tas- 
seling than would be the case with either sulphate of am- 
monia, or organic nitrogen. 

Some difference of opinion exists as to the amount of nitrate 
that can be judiciously added to the soil, and reference will be 
made to that subject later on. 

Attention has been called to the fact that where nitrate of 
soda and chloride of potash are applied to the same land, a 
chemical reaction might ensue to the detriment of the soil. 
This supposition is based on the fact that the solium of the 
nitrate of soda has a strong affinity for chlorine, which forms 
a part of the chloride of potash, and that the two elements 
might combine with each other to form common salt. Al- 



16 

though this icactioii is within the roalm of probability we are 
without the necessary data for a contirniation of tliis view. 
However it is better to be on the safe side, and on aeeount of 
this probable interchange of elements to use potassium sul- 
phate instead of potassium chloride, where nitrate of soda is 
being used on the land. 

Sul])hate of ammonia on account of its ready solubility, and 
small liability to waste as com})ared with nitrate of soda, is 
held in much favor as an economical nitrogenous compound. 
At IS'' C. !.:> parts of water dissolve one i)art of sulphate of 
ammonia and it is seen that little ditference exists between its 
solubility and that of nitrate of soda, rendering its diffusion 
throughout the soil almost as c(mipiete as in the case with the 
latter substance. However it has one very strong advantage 
over the nitrate of soda, in its ready ability to beconu^ fixed 
in the soil, and on that account alone, its })articular suitability 
for sonu^ locations is very ai)pai'ent. If we refer to the results 
previously given as to the comi»arativc wasti^ of the two fer- 
tilizers under similar conditions, a striking contrast is noted. 
Of 200 grams of this material added to the land in the lysi- 
meter tests only 3.52 grams of its nitrogen was lost in drain- 
age Avaters, as comi)ared with 72.5(> grams of nitrogen h)st 
from an e(}ual amount of nitrate of soda. Of this small loss, 
3.08 grams were in the foi-m of nitrate, into which condition 
it had been converted by the nitrifying bacteria of the soil as 
previously mentioned. Only .44 gram of nitrogen escai>ed in 
the f(U'm of sul])hate of ammonia. 

To show Mr. Oi'awh'y's experience with this salt on "sandy 
soils," we will gi\e his detei-minations in full, the conditions 
of his experiuKmts having been described on page 13. 



17 



Amount of moisture in 
the original soils.. . . 

Carbonate of lime in 
the soil 

Weight of soil taken. . 

Time required to pene- 
trate two feet. . . . 

Total water passing 
through 

Time required for the 
above water to pass 
throTigh 

Water holding power 
of the soils 

Moisture in soils after 
ten days 

Sulphate of ammonia 
lost 

Muriate of potash lost 

Sulphate of potash 
lost 



3.73 p. ct. 2.03 p. ct. 1.08 p. ct.! 0.61 p. ct. 



7ll5p. ct. 77.37p.ct. 81.85 pet. 
365 grs. j 407 grs. I 362 grs. 



55 min. 
320 ce. 

335 min. 
49 p. ct. 
31.5 p. ct. 

8 p. ct. 

None. 

None. 



19 min. 
342 cc. 



12 min. 
345 cc. 



180 min. 95 min. 

39 p . ct. 43 p. ct. 
20.4 p. ct. 18 8 p. ct. 



42 
44 



p. ct. 59 
p. ct 56 



p. ct. 
p. ct. 



p. ct. i 25 p. ct. 



91.07 p. ct. 
374 grs. 

8 min. 

355 cc. 

95 min. 
38 p. ct. 
16.6 p. ct. 



86 
65 

28 



p. ct. 
p. ct, 

p. ct. 



"Nitrate of sdda practically all was lost, tliore bein<i little- 
(litlereiice in the various soils."" It will be seen that where 
the lime carbonate of the soil amounts to 71.15'/ only X'/ of 
tlie suljdiate of ammonia \\as h)st. but the loss increased rap- 
i<lly in ])i-o]»ortion as the content of lime carbonate^ became 
!arji(^r, a soil of !ll.(l7':r of lime carbonate only retaining- 14;/ 
of the ammonium sulphate applied. These are unusual soils, 
lioweAer. and the projier conditions for holdin<4 the salt in 
(pu^stion ai-e notably lacking; but they att'oid us a proper 
realization of the su])erior pow<M- held by ammonium sulphate 
to become tlxed under the most adverse circumstances. In 
the last column it is seen that one soil is conij>osed almost 
entirely of coral or lime-stone, and that other in<;i-edi(Mits must 
be present in veiy snuill (piantific^s. As the double silicates in 
the land are most probably responsible for the tixinji of the 
ammonia radical, it may b(^ easily understood why the co 
efficient of tixation will be reduced in propoi-tion as the bulk 
of the soil is laken up with carbonate of lime, and the silicates 
excluded. 



18 

As regards the action of aninionirim sulphate as coiupared 
with nitrate of soda on the lime of the soil, there is a marked 
difference in faAor of the former. In the Ivsimeter tests to 
determine this point, it was found that whereas 20.52 grams 
of lime were lost through the action of the nitrate of soda aj)- 
plied. only 5.40 grams were removed through the influence 
of the sulphate of ammonia. In making these comparisons, 
attention should be drawn to the amount of lime that was 
carried from the soil by the application of water alone with- 
out the addition of the various salts. This amount was 1.72 
grams, and shouhl be subtracted from the weights of lime re- 
moved, as given in the table on page 14, in order to reach the 
actual amounts of this soil element that were lost through the 
influence of the several agencies. 

The action of ammonium sulphate in the soil in furnishing 
nitrogen to the cane, is considerably different from that of the 
nitrate. The latter substance is in a suitable condition to be 
absorbed by the plant roots immediately on going into solu- 
tion in S'oil water, or in coming in contact with the plant root 
acids. The ammonia of the ammonium sulphate on the other 
hand has to be oxidized by soil bacteria and changed into 
niti-ic acid before it reaches an assimilable state for the cane. 
This difference in the immediate availability of the two com- 
pounds will explain to a large extent the several ditferences 
disjdayed in theii- effects upon the crop. The nitrogen as 
nitrate is so readily absorbed when applied to the land as to 
act like a stimulant, while the more slowly acting nitrogen 
of ammonium sul[»hate is yielded more gradually as a plant 
food, and forms a longer lasting supply of this material, per 
given weight of ammonium sulphate added than that from the 
nitrate of soda. 

We now come to a consideration of nitrogen as supplied 
from organic sources. The chief nitrogenous substances of 
this order as ai)i)lied to Hawaiian soils, are dried blood, tank- 
age, and fish scrap or "fish-guano." Of these materials dried 
blood unquestionably ranks first, both in its high content of 
nitrogen and the ease with which it is rendered available bv 



11) 

the niici'o-oijiaiiisins of the soil. Tii a jterfectly dry state it 
lias been known to inn as liinh as 14 ])ei' rent of nitrogen. 
The sain])les of tliis malerial r<M'eiv(Ml at the Experiment Sta- 
tion would indicate an aveia<>e of about 12 i)er cent., with a 
small amount of water. 

Tankage, though containing less nitrogen than the blood, 
is an organic source of nitrogen of no little value. It is oom- 
])osed of scraps and fragments of flesh which have been dried 
and ground, after the removal of fats by steaming. Tankages 
have been received at the Experiment Station for analysis 
which were found to have as high as 10 per cent phosphoric 
acid in addition to their liberal content of nitrogen, which 
gives them added value as fertilizing compounds. 

Fish scrap, on the average, contains about 8 per cent of 
nitrogen and 7 per cent of phosphoric acid. It constitutes the 
ground residue of fish from which the fats and oils have been 
largely removed, and varies considerably in its value as a 
manurial substance. Occasionally sam})les are met Avith 
which contain a large amount of fatty matter, and tliese fats 
and oils Avhen present in considerable quantity cause the otlier 
organic matter to decompose with great difficulty in the soil. 
Some years ago a sample was received at the Experiment 
Station laboratory which was found on analysis to contain- 
over 24 per cent of total fats. 

In the consideration of organic substances as a source of 
nitrogen, a distinct difference is manifested between them and 
the soluble chemical salts which have just been discussed. 
Nitrate of soda and sulphate of ammonia, on account of their 
solubility in water, may be readily taken up by that medium 
and distributed throughout the mass of the soil. The organic 
material on the other hand can only be applied to the land in 
spots and needs slight covering to depths varying with the 
nature of the soil and of the substance used, in order that 
the most suitable conditions will be reached for thorough de- 
composition and nitrification. 

Nitrification is believed by many authorities to be accom- 
plished through the agency of three kinds of soil bacteria. 



2(1 

One kind chanjies the nitrogenous material into aninioniuni 
compoundis, another eonA'erts The hitter into nitrons acid, and 
still another completes the work by a conversion from nitr<»ns 
into nitric acid. These processes are slow and in the conrse 
of their ()i>eration a gradual distribution of soluble ammon- 
ium comi»ounds and nitrates throughout the entire soil veiy 
probably takes place. For instance as tlie ammonia is formed 
it may be taken up by the water of the soil and carried som<^ 
little distance before it becomes fixed, and on being oxidize<l 
into nitric acid a further dissemination most likely results. 
The extent of this gradual distribution <-annot be measured, 
but that available nitrogtMi is cariied to ]»arts of the soil 
i-emote from the j)oin1 of contact of the original substance is 
unquestionable. 

1N)TASH. — This element is usually piesent as sulphate of 
potash in Hawaiian fertilizers, although the muriate is also 
used to some extent. Th"-" sulphate on account of its very 
small etlect upon the lime of the soil is favored more than 
the muriate, and as littie dltference exists between the pricc^s 
of the two compounds, the former proves very often the more 
economical in some localities. 

Owing to the iai»idity in which jxttash becomes fixed in 
loams or soils of a clayey nature, Dr. Stubbs of the Louisiana 
Experiment Station believe-i that, in son)e instances, the more 
proper time for application would be before ])lanting, in order 
that the repeated plowing and harrowing might thoroughly 
distribute the element throughout the soil; otherwise if usetl 
as a top dressing it might become entirely fixed in i)laces con- 
tingent with the point of application. However, on account 
of the basic nature of Hawaiian soils, and their snuiller con- 
tent of double silicates as compared wilh Amei-ican soils as a 
rule, potassi(- fertilizers are much mor(^ readily disseminated 
throughout the soil mass by means of rain or irrigation water. 
In fact, in the lysimeter tests conducted at the Experiment 
Station, it Avas shown that }»otash was found in the drainage 
waters where excessive irrigation was followed, and in 
amounts sufficient to indicate a loss of the potassic fertilizers 



which had bwu apjtiicd to I lie soil. Data ai-c hiciviiiji' 1(» indi- 
cate the relative fixiiiji ])<)\vei- of porash in the two salts under 
consideration, but fij^niM's may be found in the table on page 
14 to show tiie inrlnence exerted hx each form in removin>'' 
lime from the land. It is seen that nearly nine times as much 
lime was removed from the land where muriate was added, 
than resulted from the application of sulphat(\ The influence 
of }»otassinni chloride is evidently almost as i»ofent as that of 
the nitrate of soda in its dei)leting- action on the lime content. 

In ^Ir. Crawley's invest igations with the "sandy soils" pre- 
viously jeferred to, some very surprising results were reached 
as ]-egards the disposition of the respective ])otassic com- 
jiounds to become fixed under similar conditions in soils of a 
highly calcareous nature. By )-ef erring to the tabulated re- 
sults on page 17 it will be noticed that none of the chloride or 
sulphate of ]>otash was lost in the soil containing flie least 
amount of lime carbonate. In fhe soil with the highest per- 
centage of lime carbonate. (■»') per cent of the chloride was loK-t 
and 2S per cent of the sulphate. The absorption of potash by 
these peculiar soils is intluenced chiefly by their content of 
lime carbonate for several reasons. The higher the percent- 
age of lime carbonate the lower must be that of the double 
silicates in the respective soils, as was pointed out before in 
considering sulphate of ammonia, and these silicates are par- 
ticularly instrumental in holding potash. The mechanical 
condition of the soils is intluenced to a large degree by thi^ 
quantities of lime carbonate that the}- contain, and as the 
mechanical condition varies so will the rai)idity with which 
a solution may filter through them. The time that the solu- 
tions of potash were in contact with the earth in the pipes in- 
fluenced in great measure the extent of the resulting chemical 
changes. 

In the early rej)orts of the Experiment Station it was point- 
ed out that in adding chhuide of ]»otasli to lands bordering on 
the sea and which are sometimes abnormally high in salt, 
there is a liability of inci*easing the proportion of this deleter- 



22 

ious substance, and on that account sulphate of potash was 
advised as the proper form under such conditions. 

Phosphoric Acid. — This element exists in fertilizers in 
many combinations with varying degrees of solubility. It is 
usually classed as water-soluble, citrate-soluble, or insoluble. 
In considering the availability of what have been called the 
essential elements of the soil, it was noticed that although the 
lands of the Hawaiian Islands are usually very high in phos- 
phoric acid, that very little of it is rendered assimilable dur- 
ing the growth of the crop. On that account it would seem 
most natural to apply this element in its most soluble form. 

The water-soluble phosphoric acid in the form of super or 
double super:plios})hate is readily taken up by rain or irriga- 
tion water and distributed more or less throughout the sur- 
rounding soil and is rather thoroughly tixed. This fixation is 
brought about by the carbonate of lime and by the hydrated 
ferric oxide and alumina present. In the first case, a more or 
less insoluble phosphate of calcium, and in the second case 
a basic phosphate of iron or alumina is produced. Although 
there are Hawaiian soils with no inconsiderable amount of 
lime carbonate, the great bulk are either lacking in that com- 
pound or else contain it only in very small i)roportions. The 
ju'edominating bases are those of i''on and alumina, and with 
them the phosphoric acid is rather quickly united; even where 
calcic phosphate is formed the indications are that the phos- 
])horic acid of this substance is gradually yielded to form com- 
binations with the former. As nearly all the phosphoric acid 
in the island soils is already a component part of these basic 
phosphates, it would seem on first consideration that little or 
no improvement could be etfected by a further addition to 
these insoluble compounds. However, when the soluble phos- 
l)hoi'ic acid is taken up by the water in the soil it is distrib- 
uted thoroughly and coming in contact with the minute part- 
icles of iron and alumina, results in compounds which on ac- 
count of their existence in extremely snuill grains, and on 
account of their thorough dissemination throughout the soil 



28 

mass, are in a niiuh iiioic available conditiou than the natural 
basi<- phosphates of the land. 

('itrate-solul)le, or di-calcic }»hosphate. althoujih insoluble 
in water, is soluble in a solution of citrate of ammonia, and is 
readily absorbed by the acids of the plant roots. Owing to its 
insolubility in water, however, it cannot be so thorouj;hly in- 
corporated with the soil, as the form previously described and 
is of corresponding less value. 

By insoluble or tri-calcic jdiosphate is meant that form 
which exists in natural or untreated phosphate, and is in 
soluble in water or citrate of ammonia. In the soil it is ren- 
dered slowly available through the processes of decay or de- 
composition, which action is influenced by the amount of 
organic matter with which it is associated, the fineness of its 
mechanical division, and also by the moisture content, depth, 
and temperature of the soil in which it lies. Dr. Maxwell 
has pointed out that the acidity of a soil also assists material- 
ly in this decomposing action, and attributes the greater effect 
of bone meal on some of the u])lands to the higher moistur«^ 
and acid content of those soils as compared with the lands of 
a lower elevation. 

Lime. — This element is present in nearly all fertilizers con- 
taining phosphoric acid, and as calcium phosphate is added in 
large quantities to Hawaiian soils. In addition to the lime as 
I)hosphate a considerable quantity is also present as sulphate 
or gypsum in treated phosphates such as the form designated 
as water-soluble or citrate-soluble, and on account of its fine 
mechanical and chemical condition is of high value as a fer- 
tilizing ingredient. 

(xround coral and coral sand are also good as well as chea]) 
sources of this element and are used to a considerable extent 
on these islands, especially where the content of organic mat- 
ter is low as well as the lime. The percentages of lime in the 
various compounds are approximately as follows: 

(iypsum 32 per cent of lime. 

Ground coral 45 per cent of lime. 

Coral sand -19 per cent of lime. 



24 

The ditterenoe in lime content between coijil sand and 
jiTonnd coral is due to the admixture of shells in the former, 
which are c()ii:]»oscd of almost ])ure lime carbonate. Slaked 
as well as quick lime are used in some htcalities, but owinji to 
the readiness with which these forms of lime attack the nitro- 
genous }naterial of the soil, the.v are unsuitable for many 
lands. 

Feutili/eks Tsei) ox the Diffekext IsLAXits. — The amount 
of fertilizer to be added to any land involv(^s a consideration 
of the available constituents of the soil, and the demands of 
croppinji;. Tln^ foini in which its iniiiedients should exist is 
inrtuenced by a consideration of their resi»ective properties 
and the existini*' clinmtic conditions of the localities in which 
they are to be applied. 

On the Island of Oahu, the averaj^e mixed fertilizer con- 
tains its phosphoric acid in the water-soluble and citrate 
soluble forms; the potash is in the form of sulphate; and the' 
nitrogen is applied in three forms, as nitrate of soda, sulphate 
of ammonia and organic material. 

On Maui, fertilizers are api)lied to a large extent in the 
same forms as on Oahu, the water-soluble and the insoluble 
phosphoric acid being somewhat lower. The three forms of 
nitrogen are generally used in the same fertilizer, although 
nitrogen as ammonium sulijhate is in excess of the organic 
and niti-ic. The total nitrogen is ().('» per cent higher than on 
Oahu. 

On Hawaii on account of the diversity of conditions, fertil- 
izers are naturally found to vary more in their composition 
than on the other islands. In the Hilo district owing to the 
heavy rains, nitrate of soda cannot be used without liability 
to waste, and potash in the form of chloride is in disfavor 
owing to its depleting action on the lime content of the soils 
which are already low in that element. Most of the nitrogen 
used in the district is derived from organic sources and also 
in some measure fi'om sulphate of ammonia, although some 
few fertilizers used during the past year contained nitrate. 
In Hamakua phosphoric acid is applied mostly in soluble 



foiins, the uihoiicn as a rule bcinu dciivcd fioin ainuioiiiuui 
sulphate and the potasli froiu sulidiatc. 

Oil Kauai, nitrate of soda and snli)harc of ammonia are fav- 
ored as sources of nitrojicii for mixed fcrtiliz(M's, very little 
of tliis clement beinj^ ajtplied in an organic form. According 
to the analyses of the Experiment Station laboratory, Kauai 
fertilizers are higher in nitrogen as a rule than those from 
an;.' other island. 

On aci'ouiit of the wide \aiiaiions in the composition of fer- 
tilizers and tile limited number at hand for forming an esiti 
mate, it would be impossil)le to give average formulas for the 
differeiil islands which would be leliable for juirposes of com- 
parison. The following table will give an idea of the wide dif- 
ferences between the lowest and highest ]>ercentages of each 
element a]t])lied in mixed fertilizers of which we have data. 



Island. 


Potash. 


Phosphoric Acid. 


Nitrogen. 




Lowest 


Highest. 


Lowest. ! Highest. 


Lowest. 


Highest. 


Maui 

Kauai 

Hawaii . . 

Oahu 


Per Cent. 
4.J3 
4.89 
4.03 
8.50 


Per I'ent 
17.24 
10.10 
22.54 
14.66 


Per Cent 
5.10 
5.68 
5.29 
7.01 


Per Cent. 

14.26 

9.39 

14.61 

15.00 


Per Cent. 
5.04 
6.66 
3.25 
4.7(1 


Per Cent. 

9.70 

9.91 

10 42 

7.10 



Time and Mkthoks of Aiu'Lvrxc. — Theoretically the various 
elements should be added to the laud in such ]>r<)portions and 
at sueh times as Uw cro]) leiiuires them. This would nece^;- 
sitate repeated applications of small quantities of mixed fer- 
tilizers with their respective ingredients in ever varying pro- 
portions, due consideration being given to their individual 
inclinations to Avaste. It would mean the feeding of the plant 
according to the needs of its tiuctuating growth and develop- 
ment, and the multitudinous changes involved in the elabora- 
tion of its products. Agricultural science has not advanced 
so far as to make such nice calculations possible, and if it 
had. the cost of labor would not permit the close application 
of such theoretical doctrines. 



26 

Most plantations make two applications of mixed fertilizers 
during the growth of the crop and the times of these applica- 
tions vary on different plantations. Some incorporate fertil- 
izing material with the soil of the seed bed before planting 
and others make the first application when the cane is six to 
eight weeks old or after suckering has actually commenced. 
Where two applications are made, the first is usually at the 
end of the suckering period and the second in the fall or in 
the following spring, depending on the time of the planting 
season. 

The methods followed in applying fertilizers depends large- 
ly upon the kind used. Where the ingredients are in soluble 
forms, on account of labor considerations the practice on 
many plantations is to merely drop the material in the fur- 
row beside the cane stalks, without covering. This method 
should give satisfactory results with any but fertilizers con- 
taining organic and insoluble forms such as blood, tankage, 
etc., which latter substances require a slight depth in the soil 
to meet the proper conditions for nitrification and satisfactory 
decomposition. 

Dr. W. C. Stubbs, ("Sugar Cane," Vol, 1) says, in speaking 
of practices in Louisiana: "Nitrates and salts of ammonia 
are always best used as a top dressing — at short intervals, in 
small quantities. Dried blood requires but little depth, pro- 
vided moisture necessary for conversion into available plant 
food be present. Tankage, bones, and fish scrap must be sunk 
to deeper depths to obtain fermentation necessary to their 
conversion into soluble plant food. None of the above should 
be turned too low, especially in stiff soils, since air, moisture, 
and heat are the factors needed in decomposition." 

It was pointed out in the report of the Experiment Station 
for 1890, that considerable risk is entailed by applying soluble 
fertilizers in the furrow under the seed where irrigation is 
practiced. Under such conditions there is a likelihood of the 
material being washed down and out of the soil before the 
young cane is in a condition to appropriate any of it. This 
would not apply, however, to organic sources of nitrogen or 



27 

phosplioi'ic- acid which arc so gradually decomposed, and we 
understand tliat such material is giving good results in one 
locality when applied in such manner. 

Mr. Geo. Eoss, member of the Committee on Fertilization, 
writes a very interesting letter on the practices followed on 
Hakalau Plantation. He says: "At Hakalau I am u»ing al- 
most exclusively a high grade fertilizer of the following aver- 
age composition. Nitrogen (from sulphate of ammonia and 
organic ammonia of dissolved bones) 5 to 6^; Phosphoric acid 
(available) to 10 ^: Potash in the form of sulphate of potash, 
9 to 10;/. This is applied to the plant cane at the rate of 900 
lbs per acre in two applications, the first at time of planting 
and at the rate of oOO lbs. per acre, scattered by hand in Ihe 
bottom of the furrow, or seed bed, followed by a cultivator To 
stir it up with the soil. The second application is at the rate 
of fiOO lbs. per acre and just prior to 'hilling up,' or when the 
cane is too high for further cultivation by mule or horse im- 
plements. At this time it is scattered, also by hand, on both 
sides of the cane row and covered up by small plows which 
throw the soil in towards the cane, which is afterwards 
trimmed up by the hoe. 

The same grade of fertilizer is applied to all ratoon cane, 
but usually in one application of about 500 lbs. per acre. It 
is applied to both si^es of the row as is done in the case of 
the second application to plant cane, and is covered over i.i 
the same way by small one horse plows. The usual practice is 
to apply it to the ratoons as early as possible after the lirst 
hoeing. 

We have used a fertilizer of this general composition for 
several years, and although I have experimented to some ex 
tent with such special fertilizers as tankage, fish scrap, and 
bone meal, I have had no results to warrant their continuance. 
Nitrate of soda on account of its solubility is not adapted to 
this district, where in the past we have been subject to s'lch 
heavy rainfall whereby this salt is liable to be lost before be 
ing taken up by the plant. Lime always gives satisfactory 



2S 

results and this is tnie of all soils in this district. Filter-press 
cake when passed thi-ough a disintegrator and ai)plied in lib- 
eral (|nantity gives excellent and lasting lesults. The same, 
of course, is true of stable manure. I might state that tlie 
percentage of jjotash in the mixed fertilizer, above refem^d to 
was increased from 5 to 6''/ uj) to its present strength about 
three years ago, and with marked i-esults. This was suggest- 
ed to me frou) obsei-ving the luxuriant growth produced by 
ashes fi<nn timber bui-nt in forest clearing." 

On sonu' planlations a most commendable systmn is fol- 
lowed of modifying the com])osition of fertilizers to suit the 
recjuirements of the ditferent fields. ^Ir. I). (\ Lindsay, of 
]*aia Plantation says: '"Our regular ]»lant cane mixtuie is 
com])osed of su]>er-](liosphate, sul})hate of i)otash, nitrate of 
soda and sulphalc of annnonia. ^^'e have each held we plant 
analyzed and vary the ])ro])ortions of the above ingredients to 
suit the analysis, so that as a rule every held has a ditferent 
fertilizer to suit its requircnnuits. 

A\V sometimes use as a si)ecial fi^rtilizer a mixture of nitrate 
of soda and coral lime in equal (juantities and ai)i)ly about 400 
to 500 lbs. ])er acre. We ai)i)ly this as late as July ;u)d 
August in the same manner as plant cane mixture. 

The dif[Vrence between our plant cane and ratoon mixture, 
is. that in the latter we increase the projiortion of nitrate of 
soda and deci-ease the phosphoric ingredient." 

Mr. John A\'att of the Committee on Fertilization, in writ- 
ing concerning the ]>ractices followed at Honokaa. says that 
it is custonuiry to a])])ly from .500 to SOO ]>ounds of mixed f<'r- 
tilizer per acie for the croj). "On poor upj)er lands we give- 
two ap])lications, on lowei- lands wheri^ soil is rich we give 
only one. AX'ith only one ajtpli cation we distribute the fer- 
tilizer in the fui-row before the S(vd is put in, mixing with the 
soil by a subsoiler or small ])]ow. \Miere we give two ai»pli- 
cations the first is given as above and second is given Avhen 
the cane has about two months' gi-owth, sometimes a little 
later dejjending ui)<)n the condition of the cane, by distribut- 



21) 



in^ tho tVitilizei- aloiiii side of Tlic stool and cillicr lioriuy it 
in or ruiiniiii; a ciiltivatoi- alon^ tli<- fnn-ows.'" 

This yeai- tlu' jiciicral coniiiosition of niixed fcrlilizei- ap- 
plied at Hoiiokaa has hcci! as follows: 

'.) — 1(1;/ I'hosphoric acid. 

8f/ Aiinuoiiia fioiii siilphat(\ 
5^' ]*()tash from snljdiare. 

]\Ir. AVatt says; "The above is the fertilizer which we have 
used this year and the weather has been so that we cannot 
tell what results we nuiy have from it. T.ast yeai- we used a 
ditferent mixture ou the upper lands with veiy ^ood results, 
the jinalysis of which was as follows: 

15;/ Potash fr(»ni sulphate. 
5;/ Ammonia fi-om sul])iiate. 
10 — 12;^' IMiosphoric acid. 

"With the above fertilizer the cane came up very well and 
nuiintained a vigorous growth until it was clucked by th(^ 
very dry weather durin<;' the past five months. When we 
planted this cane we ^ave it an application of 70(1 pounds of 
the above fertilizer with the seed and about foui- months later 
w'e gave it 700 ])ounds ])er acre more." 

For some years ]»ast Mi'. Watt has beiui very careful in 
regard t(» the })reseiviug (*f all stable manure, which is liber- 
ally treated with a dressing of sui)erpliosphate to pr(^vent loss 
of ammonia. Both with this comjtound and with mud-press 
cakes which have l)een ])assed through a disint(^grator hi^ has 
obtained si)lendid results. 

\W are in rect'ij)t of a very interesting letter from Mr. J. T. 
Crawley, who writes of a method in vogue at Kilun IMantatiou 
for tlu^ distribution of nitrate of soda. Ou account of its bear- 
ing so strongly ou the (juestion of labor economy the letter 
is given in full. 



30 
Honolulu, T. H., Sept. 24, VM)1. 

€has. F. Eckart, 

(Miaii'man, ("oinniittee on Fertilization. 

I3kau Sik: — I wish to inclnde in tlie lepoit on fertilization 
a method of applying nitrate of soda devised and used by 
Manager W. F. Pogue of Kihei Plantation, and eonmiunieated 
to nie in a letter from him dated July 2(>. ]Mr. I'ogue says: 
''Lacking labor suftieient to apply nitrate of soda with ground 
eoral, I hare just finished fertilizing some (iOO odd acres with 
nitrate dissolved in water and applied in the irrigation. The 
form of application was as follows: Dilute one bag of nitrate 
of soda in one barrel containing 50 gallons of water, one pail 
of this solution is added to 4 pails of water, or in that pro- 
portion; in another barrel a hose bibb in the bottom of the 
last barrel discharges the diluted solution into a tub which is 
kept filled to a given mark, from the tub the mixture flows 
in an exact amount all day into the main irrigation ditch. The 
outlet of the tub is fixed, and cannot be opened or closed by 
the laborer doing the work. Strainers are used on the tub 
and diluting barrel. In this way one man can easily apply 
100 lbs. per acre of nitrate to 00 acres in six days, two men 
will do three or four times as much. In applying I have put 
on 75 lbs. of nitrate to an irrigation, then skip one or two 
irrigations and apply the same amount again. 

The fields thus treated have started from short jt)int sticks 
to very long joint sticks which means a very rank growth. 

It seems to me that any soluble fertilizers can be applied 
much more evenly and certainly vei'y much cheaper than in 
the ordinary method. 

It also seems to me that if the applications could be made 
in small doses as the cane needs it, it would be the correc-t 
method, exactly as we would feed a horse or a cow." 

Again in a letter of Sept. 20, Mr. l*ogue says that he is 
applying 50 pounds nitrate per acre. To quote his words: 
"^^'e have with my method applied 50 i)Ounds to the acre with 



31 

one pidinary Jap to as high as 26 acres in one day, that is, 
5,250 pounds were applied to 105 acres (one field) in four days 
by one Jap. The cane began showing the eftects on the fiftli 
day, by the seventh day after application, the cane roots had 
fully gotten hold of the stimulant, from a greenish yellow the 
leaves were turned a dark green. 

We apply 50 lbs. nitrate every other irrigation, or say every 
IS days. Cane shows the want of stimulant in from 20 to 30 
days, according to nature of soil, after first application, and 
30 to 40 days after the second application with this amount 
of 50 lbs. per acre. Later on, I can give aou results of further 
experiments on these same lines." 

The idea of dissolving the nitrate of soda in the water of 
irrigation was suggested by the scarcity of labor, and Mr. 
Pogue saw the added advantage of applying this very soluble 
fertilizer in very small quantities and frequently, rather than 
in one or two large doses. The only objection that I can see 
to this method is that there will be loss in the ditches through 
which the water passes before it reaches the rows of cane, and 
this loss will depend upon the nature of the soil that compose 
the bottoms and sides of the ditches. Mr. Pogue states that 
in the red soils where he is using the method the loss of water 
is very small. Again, if the part of the row where the water 
is entering takes up more water than the far end it will like- 
wise take up more nitrate of soda. 

The main advantage, aside from the labor question, to my 
mind is the advantage of applying only so much nitrate as the 
cane needs at the time, and to be able to apply it in small and 
frequent doses. 

With as fugitive a substance as nitrate of soda this is a 
great consideration indeed. \Yhatever of this substance as is 
not taken up by the cane, can be washed away either by a 
heavy rain or by a heavy irrigation, and the least amount that 
is in the soil at any one time the less is the danger of loss. 
Very truly yours, 

J. T. Crawley. 



32 

This method for the distiibntiou of nitiate of soda, as 
adopted by Mr. Po^ue, apparently has much to commend it, 
both as regards the saving of hibor and the added advantage 
of being able to apply small quantities of the mateiial as the 
cane seems to demand it. As the barrel from which the 
nitrate solution is discharged into the main ditch is- kept at 
a constant level, an even pressure and discharge is obtained 
which would guarantee a regular and unchanging admixture 
of nitrate solution and ii'rigation water. Mr. Crawley's obser- 
vation as regards probable loss of nitrate during the passage 
of the water through the irrigation ditches is well taken, 
though this loss may probably be small and of little conse- 
quence as comjjared with the saving of labor and other ad- 
vantages to be derived from a following of this method. How- 
ever this loss is a factor which will be considered later on in a 
special reference to the use of nitrate on plantations. 

A curious jioint manifests itself in this method of ai)plying 
nitrate of soda, which would be particularly striking where 
the cane is jdanted in long rows receiving their water direct 
from the main ditch, and less so in proportion as lateral 
trenches are used and the cane rows shortened. In the former 
instance the ends of the rows next to the ditch necessarily re- 
ceive more water than the other extremities and consequently 
they will receive more nitrate. When this material is dis- 
tributed in the usual way by hand, each part of the field has 
approximately the same amount applied to it, and loses it in 
proportion to the amount of water added providing a point 
above saturation is reached. At the ditch end of the furrow, 
according to Mr. Pogue's method a larger quantity of nitrate 
comes in contact with the cane roots, while in the ordinary 
method that point is marked by the greatest loss. 

Mr. Pogue sjieaks of the probable advisability of applying 
all soluble fertilizers in this way on irrigating plantations and 
the plan certainly presents many favorable points for consid- 
eration. However, the question would arise whether the sav- 
ing of labor and the advantage of small and frecpient applica 
tions would otf-set tli<' loss of soluble high urade fertilizers 



35 

in tlic iiiij^alioii ditches^ which is inHiieiiced by the area and 
iiatnie of the exposed soil. This is a point which must be 
studied out \ery carefully before any radical change in the 
system of applying fertilizers is introduced, and I believe this 
point may be fully determined by a method which will shortly 
be presented for consideration. 

It has been pointed out that the ends of tlie furrows next 
the ditches receive more water than other points along tlit 
cane row. Under ordinary conditions the soil at these furrow 
ends, where long rows are the rule, will soon become sat- 
urated and lose a larger (piantity of their available plant food 
ihan other points, through the hnuhing action of the excess 
of water. With that water will go a certain i)ercen1age of the 
fertilizer in soluti()n it is true, but the dissolv(Ml elements 
which leave the irrigation watei- to become^ tixed in the soil, 
would doubth^ss be more than snfticient to i-eplace the same 
elements that had been remoNed from the soil itself. In other 
words the largest amount of fertilizing mateiial would be 
added to the p(»ints sutl'ering most from ordinary iirigation, 
on account of the resultant leaching action. 

XITKATE OF SODA. 

Owing to the differences of opinion held by plantation man- 
agers concerning the eflicacy of this substance as a fertilizing 
compound, I wish to give a consideration of this subject some 
I)rominence in this i-eport on fertilization, as I believe that the 
reasons for this dirt'ei*ence of opinion can be largely explained. 

Jn th(^ early re])<)rts of th<^ Experiment Station, the readi- 
ness with which nitrate of soda is taken u]) by the cane and 
its corresponding stimulating action on the i»lant were re- 
ferrt^l to at some length, ^^'e may quote from the Keport of 
1805, page 20, where Dr. ^Maxwell says: "Excepting in loca- 
tions where the water supi)ly is so small as to retard its (piick 
operation, nitrate of soda is not a safe and normal fertilizer — 
it is not a good ordinary diet for comparatively slow gro\\ing 
])lants. T'nder the average conditions of moisture and 
warmth, the plant takes it too greedily, and tlu^ result often is 



34 

abnormal growtli. The results of this abnormal growth in 
cane are bulk, which includes an excess of water and un- 
elaborated products of assimilation, and comparatively less 
sugar, with low purity of the juice. In wheat and oats the 
result is lots of straw and little grain. In one case where the 
manager of a i)lantation called my attention to a piece of 
cane, which he called 'very coarse and rank, and would never 
get real rij)e,' I found that Ii5() pounds of nitrate had been 
added all at once, and the weather had been such as to allow 
of the fullest effects. I do not advise nitrate of soda as a reg- 
ular diet in any situations excepting those of extremely small 
water supjjly. I advise nitrate of soda only as a tonic and 
immediate source of nitrogen in a crisis of a crop, and only in 
locations of moderate or small rainfall, but never wiiere th(^ 
rainfall is constant or heavy." 

The views of Dr. Maxwell on this subject are clearly set 
forth, and the advices of the Experiment Station in regard to 
the use of this material have been largely influenced by his 
practical observations of field effects following the application 
of nitrate on plantations. 

During the last few months, my attention has been called to 
the fact that a number of plantations are applying nitrate far 
in excess of amounts considered safe by the Experiment Sta- 
tion for the normal growth and development of the cane, and 
reports from these plantations indicate that the cane is doing- 
well. These cases certainly need careful consideration, and a 
study of the conditions under which nitrate is applied in these 
instances must necessarily throw considerable light. on this 
important and apparently perplexing problem. Reference has 
been made to a case where 350 pounds of nitrate, per applica- 
tion ]>er acre, were seen to produce a rank and frothy growth 
on one plantation where conditions allowed its complete ap- 
propriation by the cane. In other instances of more recent 
observation it is found that 500 pounds, per application per 
acre, leaves nothing to be desired, the cane presenting not 
only a vigorous, but a perfectly sound and healthy growth. 
This apparent inconsistency, I believe may be fully explained, 



85 

and the explanation will involve a factor of j^reater econoni 
jcal significance tlian the nitrate itself, namely that of water 
sn])pl.v. 

The properties of nitrate of soda have already been dis- 
cussed, and its ready solubility and disinclination to become 
fixed in the soil have received special attention. It was noted 
in the lysimeter tests referred to on page 13 that the loss of 
nitrate of soda from over-irrif»ation reached extremely large 
proportions and thos*^ data will now be of particular value in 
considering the subject in hand. If a plantation were to use 
say 500 or (500 lbs. of nitrate, per application per acre, also 
applying mor<' water to the fields than the soil will hold, the 
excess of water which drains off is necessarily going to carry 
from the land, a large ]»ercentage of the nitrate of soda, and 
tlie nitrate remaining in the soil after irrigation is concluded 
might be easily reduced to such a quantity that a harmful in- 
fluence could not be exerted on the crop. In otlier words the 
cane would not get all of tlie nitrate applied and a large per- 
centage of this material together with a large anu)unt of 
water would be going to waste. 

It is seen that such a condition of affairs is possible, and 
with the light of further data it will be seen to be probabl(\ 
Where a plantation is using large amounts of nitrate without 
any signs of an injurious action, and where the water of irri- 
gation is practically free from salt, a view that ovei-irrigation 
is practiced can only be based on the non-deleterious action of 
the nitrate of soda; at the ]»resent time sut!1ci«Mit data for a 
thorough confirnuition of this opinion are lacking. But if we 
take a ])lantation that is using nitrate of soda in large (juan- 
tities and is irrigating with water of high salt content, suflti- 
cient evidence is at hand to show that a large part of that 
nitrate is being wasted, and in i)roportion to the amount of 
w'ater used over and above w^liat is necessary to saturate the 
soil. This leads us into a consideration of the salt content of 
irrigation water and of Hawaiian soils, which subject has a 
particular beai-ing on the question before us. 

In Bulletin No. 90, V. S. Department of Agriculture, en- 



36 



titled "Irrigation in Hawaii," is given a table showing tlie 
l)er('entages of salt that have been found in Hawaiian soils, 
and the resulting condition of cane growing on those lands. 
The tabulated results are given in full. 

SALT FOUND IN HAWAIIAN SUGAR LANDS, AND ITS EFFECT 
UPON SUGAR CANE. 



Sample 
Soil 


Location. 


Salt in 

Soil. 

Per Cent. 


Condition of Cane. 


1... 


Highlands 


.061 
.063 
.050 
.059 
.129 
.130 
.155 
.181 
.181 
.460 
.832 
.223 


Normal. 


2.... 




Normal. 


3.... 


(( 


Normal. 


4 .. 


1. 


Normal. 


5... 
6.... 


Lowlands 


Not wholly healthy. 
Not wholly healthy. 
Quite healthy and normal. 
Yellow in color. 
Yellow in color. 
Small, yellow, stunted. 
( 'ane white and dying. 
Leaves bleached, cane small. 


7. . . . 


(( 


8 ... 

9.... 
10 ... 
11... 
12 ... 


It 
Sea bluff land 



Another table gives the effect of salt upon the growth of 
cane, on ''three parts of one field which contained different 
amounts of salt in the soil, the soil in other respects being- 
identical." 



First part, . . 
Second part 
Third part. 



FIELD. 



Salt in 

Soil. 

Per Cent. 



0.10 
0.45 
1.00 



Yield of 
sugar 

per acre. 
Ton.-. 



6.0 
1.5 
0.0 



It is noticed from the first table that where the salt content 
of the soil reaches over 0.1 per cent an injurious effect is pro- 
duced on the cane, soil sample No. 7 with 0.155 per cent being 
an exception. 

We will now consider the amount of salt that is found in 
some of our irrigation waters and take for an example, the 



37 

water of a plantation which is nsing 1,000 ponnds of nitrate 
of 8oda per acre, malting two applications of 500 pounds each. 
The manager of this plantation estimates that he is using 
about 2,500,000 gallons of water ])er acre for the crop, and this 
water is found on analysis to contain over 125 grains of salt 
per U. S. gallon. If 2,500,000 gallons of water are being ap- 
X)lied to the acre, with it go 41,042 pounds of salt, during the 
growth of one crop. If the land in question were not irrigated 
to a point above saturation practically none of this water 
would drain off and the salt would remain in the soil. The 
weight of an acre of soil to a depth of 12 inches is approxi- 
mately 3,500,000 pounds, and 44,642 lbs. of salt are practical- 
ly 1.27 per cent of this amount. This would mean that at the 
end of five or six irrigations the cane would likely sicken and 
turn yellow. A certain amount of salt is taken up by the 
cane itself without ajjparent bad effects, and the percentage 
remaining in the soil would consequently be lessened but only 
to a very small degree and not enough to alter these figures 
to any appreciable extent. 

However the cane on this plantation is doing well and the 
salty water is having no apparent effect, which would indicate 
that the salt from the water is not reaching a harmful accu- 
mulation in the soil. An undue concentration of salt could 
only have been prevented by an occassional very heavy rain 
or by an excessive amount of water used in irrigation. For 
instance let us say that only so much water was added during 
five irrigations as the soil would take up and hold. Then this 
water would evaporate from the surface of the soil and be dis- 
sipated into the air through the leaves of the cane, leaving 
the salt behind, and in quantities sufficient to weaken the 
growth of the cane. If, however, for the sixth irrigation, 
•double the amount should be used as w^as applied during any 
of the previous irrigations, the accumulation of salt would 
be dissolved up and removed in large measure in the drainage 
from the land. 

The soil would then be freed from its injurious amount of 



38 

salt and ajiain be suitable for the growth of the cane. This 
occasional flushing of the land to such an extent is not likely 
to occur, however, on an irrigating plantation; the chances 
are in favor of an excess being applied at each watering, and 
that the amount that drains off from the land during every 
irrigation is what keeps the salt down below a harmful pro- 
portion. The manager of this plantation did not feel that he 
was using an excess of water, because if he decreased the 
amount applied, the cane soon showed it. Now on cutting 
that water down did the cane suffer from too little water or 
too much salt? To my mind it was more likely the salt which 
I)roduced the sickening of the cane, because conditions were 
then made more favorable for an accumulation of that ma- 
terial. 

If a soil were irrigated with saline water below a point of 
saturation, for a number of times, it has been pointed out that 
the salt solution in the soil necessarily becomes more concen- 
trated and contains a higher percentage of salt than the irri- 
gation water. Providing that the drainage from the land is 
good and an excess of water can find an outlet through under- 
ground or other channels, the more water that is put on in 
excess of the amount that the soil will hold, the more dilute 
will become the salt solution in the soil, until a point is 
reached in which the solution in the soil is practically of the 
same density as the irrigation water. The more dilute this 
salt solution is rendered, naturally the more suitable it is for 
the growth of the cane. But as soils have a high absorptive 
power for water varying on these islands between 30 and 87 
per cent., it is readily seen that after any irrigation where 
there is m.uch salt in the water, a considerable quantity of 
that material must necessarily be left behind in the land no 
matter how much water is applied. When the next applica 
tion of water is made, the concentrated solution of the soil is 
added in large measure to the irrigation applied, and the salt 
percentage of the latter is increased as it passes into the soil, 
until an amount is added sufficient to leach through the soil 
and drain off, when the dilution will set in according to the 



39 

excess of water applied after that \Hnut is reached. It can 
readily be seen what may happen when the irrigation is cut 
down in some instjinces and jtarticnlarly when it is cut down 
to such a degree as to allow of no di'ain from the laud what- 
ever. If the supply of water were decreased gradually it is 
not too much to suppose that before a point is reached at 
which the cane will suffer from too little water, it will suffer 
from too much salt. 

It has been established as a principle in soil physics that if 
a continuous and rather heavy rain falls evenly upon the sur- 
face of a homogeneous soil, a column of water is formed in 
the soil which will as it descends displace a salty solu^^ion 
without mixing with it to an appreciable extent. If the drain- 
age of the laud were good, the salt solution would be forced 
out of the soil into the natural outlet. In irrigation as prac- 
ticed on these islands, however, I believe that the ditt'usive or 
diluting action of the applied water would be a more potent 
factor in removing salt from the land, if the soil were deep 
and of high absorptive power, than that of mere pressure. 
This is caused by the water having to be distributed through- 
out the soil from fewer points of application as compared with 
rain water, and also by the fact that the salt or salt solution 
in the hills between the furrows where it is carried by capil- 
larity, could not be forced out by any column of water 
descending from the cane furrow. However, the question of 
pressure cannot be omitted entirely in a consideration of the 
manner in which salt is removed from the lands of irrigating 
l»lantations, as its importance will increase with the shallow- 
•ness of the soil and its inability to hold much water. 

We have now seen that a plantation which is using very 
salty water for irrigation purposes must have a well drained 
soil, and irrigate quite frequently above saturation, in order 
that the cane may pi-oduce a healthy and normal growth, and 
we now come to the point upon which this question of irriga- 
tion bears from a fertilizing standpoint. Under such condi- 
tions what becomes of the nitrate of soda that is applied in 
such large quantities to the land? As nitrate of soda is an 



40 

exti-einely soluble material and is but slightly fixed in the 
soil, large amounts mu^f be leached from the land and lost 
through the excess of irrigation water used under the existing 
conditions, and it is not unreasonable to suppose that the 
amount of nitrate remaining in the soil is decreased to such 
an extent, that the effects of this material on the crop do not 
correspond with the effects of the same material added in like 
quantities, but under conditions where the cane may appro- 
priate the full amount. 

These points in regard to the use of salty water on our 
cane lands open up a new field for investigation along the line 
of irrigation, but a consideration of that matter must neces- 
sarily be left out of a report of this nature. 

On a plantation where nitrate of soda is being added to the 
land in considerable quantities at each application, and where 
the irrigation water contains in solution only a very small 
amount of salt, we cannot say positively that over-irrigation 
is practiced, as at the present time data are lacking to sub- 
stantiate such a view. The fact that such land is able to 
stand more nitrate than other lands where irrigation is not 
practiced, but where the full effects of the nitrate are unques- 
tionably obtained, points to the conclusion that an excess of 
water may in large measure account for this apparent incon- 
sistency. The original nitrogen content of the soils and the 
size of the crop are naturally factors to be taken into consid- 
eration, but they are not sufiicient to account for such varia- 
tions in the behavior of nitrate as we have found in some 
instances. Unfortunately over-irrigation is not always man- 
ifested in a visible drainage from the land. An excess of 
water in some instances can sink down into a deep soil below 
a point from which capillarity can raise it, and find an outlet 
into an underground reservoir, or along impervious strata 
into the sea. 

The necessity of determining the probable loss of nitrate on 
a plantation such as we have just described would seem to be 
of more importance than in the case which has already been 
considered. Not onlv is there a likelihood of so much nitrate 



41 

being" lost, but with it is bound up the question of water 
which, economically, is a matter of greater concern. Where 
irrigation with brackish water is practiced, more water would 
necessarily have to be used, than would be the case if tin? 
water were '"sweet," as an occasional over-irrigation is re- 
quired. However, in both instances a loss of nitrate and a 
cori'esponding loss of water are conditions capable of amel- 
ioration, although the degree of conservation of brackish 
water would vary with its [lercentage of salt. 

On one plantation where nitrate is used in large amounts, 
the manager informs me that directions are always given to 
use less water for the first irrigation following an application 
of nitrate of soda, and this certainly is a good precaution to 
observe, as in a measure it constitutes a safe guard against 
the immediate loss of the nitrate. But if we look into this 
matter more closely, it can be seen that this practice does not 
insure completely against a considerable loss of this soluble 
material, although a certain saving would take place, provid- 
ing of course, that we assume that over-irrigation is the rule, 
wdiich still remains to be proven. For instance, let us say that 
500 pounds of nitrate are applied, and one-half of the water 
ordinarily used, is applied at the first irrigation following. 
Then we may feel reasonably certain that none of the nitrate 
is lost from the land during that irrigation; but the (luestion 
arises: Can the cane appropriate all of that 500 pounds of 
nitrate between the time it is applied and the second irrigation 
following? Such a period we might say would probably cover 
ten or twelve days at the most, and we may feel sure that all 
the nitrate could not possibly be assimilated by the cane in 
that time. What is not assimilated is then liable to waste 
during the second irrigation and those following. 

Although this report is concerned primarily with fertiliz<i- 
tion, owing to the manner in which soluble fertilizing material 
may be washed out of the land and lost, the question of over- 
irrigation must needs be bound up quite closely in an eco- 
nomic consideration of this subject. Through the examina- 
tion of many soils from various plantations, a wide variation 



42 

was found to exist as regards their capacities to take up and 
liold water, and consequently irrigation requirements were 
seen to vary within very wide limits in different localities. A 
comparison of the amounts of water used per pound of sugar 
produced at the Experiment Station and on several planta- 
tions, showed a variation between 859 lbs. at the Experiment 
Station and five and six times this amount on the plantations 
("Irrigation in Hawaii," Maxwell). Such results would seem 
to indicate that a superfluous amount of water had been used 
and i)robably still is being used on many plantations. This 
question from an economic standpoint is certainly one of the 
highest importance, and although at the present time we have 
data that point quite significantly to the fact that there must 
be a waste in many instances, the amount of irrigation water 
that can be applied to Hawaiian soils, without waste, has 
never been determined. The importance of the subject would 
require that a definite conclusion be reached in every case 
where the conservation of water is a vital consideration, and 
I believe that this may be accomplished in a practical man- 
ner and on the field to which the water is being applied. 

In a deep soil where the drainage is evidently through some 
underground and invisible outlet, any method for the determ- 
ination of loss of water must be based on the water absorptive 
power of the soil. If on such a land we can trace the down- 
ward movement of the water, and show that a penetration is 
reached below a point from which capillarity can raise it, the 
question of loss is fully solved. When water is applied to the 
land, it is only when the minute capillary pores of the surface 
are filled, that those immediately below can take up water, 
and on becoming saturated allow the water to proceed to 
depths below them. The downward movement of water in a 
soil is then characterized by an increasing layer of saturated 
soil which gradually extends toward the lower levels until 
an outlet is reached and percolation ensues from hydrostatic 
pressure. Now if we can follow the extension of this saturat- 
ed layer and note the time in which it comes in contact with 
a stratum or suitable medium for drainage, w^e can say pos- 



43 

itively that any water applied after such time is bound to 
waste from the hind. 

By the adaptation of an electrical instrument, termed a soil 
liygrometer, devised by the Division of Soils, U. S. Department 
of Agriculture, for determining the moisture content of soils, 
I believe the point referred to above may be fulh' determined. 
In describing this soil hygrometer we will quote from an 
article of Lyman J. Briggs, Department of Agriculture. "This 
method depends upon the principle that the resistance offered 
to the passage of an electric current from one carbon plate to 
another buried in the soil depends upon the amount of mois- 
ture present in the soil between the carbon i)lates and elec- 
trodes. This resistance is measured by a suitable instrument 
designed for this purpose. 

The electrical resistance of the soil between the carbon 
electrodes depends not only upon the amount of water present 
in the soil, but also upon the quantity of soluble salts dis- 
solved in the water, and upon the temperature. For soils lu 
which the amount of water soluble material is not sufficiently 
great to interfere with plant development, field experiments 
appear to show that for any given water content, the amount 
of salts in solution remains very .ipproximately the same in 
any given soil. The determinations made by this method rest 
consequently upon the assumption that the salt content does 
not change independently of the moisture content. Wherever 
we have a translocation of salts due to excessive evaporation 
or seepage, this assumption will not hold. In such cases the 
fact that a translocation of salts has taken place is shown by 
gravimetric moisture determinations which should be occa- 
sionally made for this purpose; and if the departure from the 
previous conditions is not great, the error may be easily cor- 
rected. 

The effect of the change in the soil resistance due to tem- 
perature is eliminated by comparing the soil resistance with 
the resistance of a small cell containing a solution whose elec- 
trical resistance changes with temperature at exactly the same 



44 

rate as the soil resistance, and wliicli is buried in the soil near 
the electrode so as to possess always the same temperature as 
the soil. 

The comparison of these resistances is made by an instru- 
ment which is a modified form of the well-known Wheatstone 
bridge method of measuring ehM-rrical resistance. The soil 
resistance and the temperature cell resistance occupy adjacent 
arms of the bridge, and any change in temperature affects 
both resistances to the same extent, and so does not change 
the reading of the instrument.-' 

''The moisture record obtained, consequently deals with the 
variation in moisture content of the same portion of the soil. 
This is one of the advantages of the method since it has been 
shown that the moisture content of a seemingly uniform soil 
nmy vary as much as 4 per cent within an area of one square 
rod. Consequently in order to obtain a consistent record of 
the change in w-ater content, it is necessary to deal with the 
same sample of soil, which can only be done by this electrical 
method." 

''We thus see that the electrical unshod has the advantage 
of working always with the same portion of soil and furnishes 
a direct and rajtid method of determining the w'ater content 
after having once been installed." 

From the above description an idea may be gained as to the 
principle of this method for making moisture determinations 
of the soil in ])lace. In adapting it to meet the requirements 
of an investigation in respect to the loss of water from the 
land, these electrodes can be sunk to varying depths in the 
soil and the movement of water can be traced. 

I believe that a number of extremely important facts may 
be learned from its use on Hawaiian plantations which could 
not be learned in any other practical way. For instance the 
amount of water that is lost in iri'igation ditches might be de- 
termined by noting the depth of soil saturation and the exteiit 
of the exposed area. The amount of nitrate of soda that 
would be held bv this amount of water, w'here that material 



45 

is a})i)lied as at Kihei, could he calculatt'd with fairly reliable 
results. 

Where irrigation with long" rows is the rule, the amount of 
water that is taken up at the ditch end could be measured and 
compared with the amount absorbed at the other extremity of 
the furrow. 

The amount of salt dissolved in waters may also be de- 
termined by this method and an insight gained as to the move- 
ments of common salt where brackish water is used in irri- 
gation. 

In fact, this method would seem to present a means of solv- 
ing many problems that have heretofore been the subject of 
much theoretical speculation, but of which our exact knowl- 
edge has been rather limited. In conclusion I will say that 
the Experiment Station is about to procure one of these soil 
hygrometers and after a thorough trial in the Experiment Sta- 
tion field I would suggest that investigations be conducted on 
the cane fields of various plantations where conditions would 
warrant the expectation that valuable results might be ob- 
tained. 

Respectfully submitted 

C. F. ECKART, 

Chairman of Committee. 



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